Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 55: Quantenpunkte und -dr
ähte: Herstellung und Charakterisierung II
HL 55.5: Vortrag
Dienstag, 8. März 2005, 16:00–16:15, TU P-N201
One-Dimensional Electronic States on Si(111)-2×1: Observation of a Coulomb Gap at low T — •J. K. Garleff1, M. Wenderoth1, R. G. Ulbrich1, C. Sürgers2, and H. v. Löhneysen2 — 1IV. Physikalisches Institut, Universität Göttingen, D-37077 Göttingen — 2Physikalisches Institut and DFG Center for Functional Nanostructures (CFN), Universität Karlsruhe, D-76128 Karlsruhe
Scanning tunneling microscopy and -spectroscopy was performed on Si-(111)-2×1 at 8 K with a spectral resolution of ∼10 mV. A disorder induced tail of the surface conduction band is observed in the surface band gap below the Fermi energy EF. At E=EF a Coulomb gap of width W of up to 150 mV opens. W scales inversely with the undisturbed length L−1 of the π-bonded chain between two monatomic steps on the cleaved surface (10 nm ≤ L ≤ 100 nm). In the case of π-bonded chains that contain a substitutional Phosphorus (P) atom, W increases according to the shortened length of the chain. The enlarged gap is found only on the individual chain interrupted by the P atom. This experimental observation excludes any coupling between neighboring π-bonded chains. Within a factor 2, the measured W(L−1) fits quantitatively to the Coulomb gap calculated from the capacitance [1] of the one dimensional (1D) segments of the π-bonded chains with finite length. The scaling W ∝ L−1 and the absence of coupling between the chains is interpreted as experimental evidence for a 1D electronic system in the π-bonded chains at low temperature T=8K.
[1] D. V. Averin and K. K. Likharev, J. Low Temp. Phys. 62, 345 (1986)